Ending months of controversy, Mayor Antonio Villaraigosa on Thursday fired Guerdon Stuckey, the city's embattled Animal Services Department chief, and replaced him with an avowed "no-kill" advocate who was just let go by New York City.

After futilely pressuring him for a week to resign, Villaraigosa handed Stuckey a letter at 4 p.m. ending his hold on the $155,034-a-year post. The 50-year-old department head has threatened to file a wrongful-termination suit.

The mayor did not comment about Stuckey, a bureaucrat who had no experience in animal-welfare issues when he was hired nearly a year ago by former Mayor James Hahn. However, Villaraigosa did release a copy of his terse, three-paragraph termination letter to Stuckey.

"This removal has been discussed with you through in-person and written communication from my deputy chief of staff and my counsel," Villaraigosa wrote. "On behalf of the city of Los Angeles, I thank you for your service."

Villaraigosa also announced he was hiring Ed Boks, the outgoing head of New York City Animal Care and Control, as interim manager, effective Jan. 3.

Boks has 22 years' experience in animal welfare and is credited with drastically cutting euthanasia rates and increasing animal adoptions in New York. Earlier this month, New York officials refused to renew his contract in what one source said was a political fight, although Villaraigosa's office said Boks had resigned.

What Villaraigosa's announcement and letter did not capture were the drama and controversy that date back to his mayoral campaign last spring, when he vowed to fire Stuckey for the city's failure to reduce the number of animals euthanized each year.

After taking office July 1, however, Villaraigosa backed away from that promise and said he would give Stuckey time to adapt to his policies as mayor.

Faced with escalating pressure from animal-rights groups and a civilian commission that often battled openly with Stuckey, the mayor last week ordered aides to meet with Stuckey and ask him to resign.

After Stuckey refused to quit and hired an attorney to help him try to negotiate a settlement, Villaraigosa fired him.

"I think it's really exciting," said Kathy Riordan, president of the Animal Services Commission. "I think good things are happening in the department. We've heard good things about Ed Boks. He's a no-kill guy."

Scott Sorrentino, president and co-founder of The Rescue and Humane Alliance-Los Angeles, criticized Stuckey for failing to implement a no-kill animal policy and said he'd alienated much of the Los Angeles rescue community.

"I'm happy that the mayor is taking the voice of the animal community seriously," Sorrentino said. "I'm glad he's taking the first proactive step in putting in place an administration that would implement a no-kill policy."

But Animal Services Department employees protested, sending Villaraigosa a letter and a petition signed by 146 employees asking that Stuckey be retained.

"To concede to the terrorists for the ousting of our general manager has placed a pall over the department and the city," the letter authors wrote. "Continued empowerment of these terrorists will only serve for them to step up their terrorist activities against department employees."

Members of more radical animal-rights groups have been accused of harassing Animal Services employees on the job and at their homes, including igniting a smoke bomb at Stuckey's downtown apartment.

The employees' letter said Stuckey has worked to improve a department that has had four general managers in five years.

"When other public safety agencies in the city get bad press or have a perceived problem, they have money thrown at them," the letter authors wrote. "We do not need another general manager. The one we have has stood up to the terrorists, focused the department (and) provided leadership and passion for saving animal lives.

"The terrorists will never be satisfied. They will never go away. It is time that you stood up to them; support your department and your fellow city employees."

Villaraigosa said Boks oversaw a massive animal-services operation in New York City, where he reduced euthanasia rates by 20 percent and increased pet adoption by 30 percent.

"Ed is committed to my goals of making L.A. a more animal-friendly city, increasing adoption and spay/neuter, reducing euthanasia of abandoned and unwanted pets, and forging strong public-private relationships," Villaraigosa said.

The mayor also named Regina Adams as acting general manager until Boks takes over next month.

Animal Services Commissioner Deborah Knaan, who is also a deputy district attorney, said she considered it time for a change in department leadership because of Stuckey's difficulty with the animal-rights community.

"We are in a crisis mode at this point and cannot afford to continue as we have been," Knaan said. "We need to bring in someone who has experience in the animal-services area and can command respect.

"It is not even a case of trying to mend relations. It is to bring in someone who will do the job and reduce killings. Actions will speak louder than words. If whoever is selected follows through on that, the community will welcome him with open arms."